Parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same

ABSTRACT

Disclosed herewith is a parallel-operated motor type stern propulsion apparatus for boats and hydraulic system. The stern propulsion apparatus includes a transom box disposed at the stern of a boat. A propulsion body situated in the transom body to be lifted and steered. The propulsion body includes an upper body supported by a lifting shaft transversely fitted into the transom box, a yoke connected to the lower body, and two lower bodies each attached to each of the lower ends of the yoke. Two hydraulic motors are each positioned in a lower body and each connected to a propeller. Lifting cylinders are attached to the transom box for lifting the propulsion body around the lifting shaft. A steering cylinder is attached to the transom box for steering the propulsion body around a steering pin attached to the lifting shaft to the right and left.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same, in which propellers are driven by two parallel-operated hydraulic motors, and the moving speed of a boat and the forward and rearward drives and steering and lifting angles of the stern propulsion apparatus are remotely controlled.

[0003] In particular, the present invention relates to a parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same, in which the control of steering and lifting angles can be performed by a hydraulic system for the stern propulsion apparatus, the mounting position of a main engine can be freely selected to allow the cabin of the boat to be conveniently designed, two hydraulic motors each having half the required capacity is parallel-operated to reduce hydrodynamic resistance, a speed-reduction and reverse device is hydraulically controlled so as to improve its durability, and the starting and stopping of the main engine, the change in the moving speed of the boat, and the forward and rearward drives and steering and lifting angles of the stern propulsion apparatus can be controlled on a control panel.

[0004] 2. Description of the Prior Art

[0005] In a conventional stern propulsion apparatus for boats and hydraulic system for controlling the same, a main engine operates a propeller via a reduction gear, a clutch, a reverse gear and a propeller shaft. Accordingly, when the propeller is brought into a submerged projection or floating matter, or seaweed or floating matters is wound around the propeller, its power train and its main engine are damaged, thereby causing a boat to run into serious danger. Additionally, a steering device for steering the boat to the right and left and a lifting device for adjusting the stern propulsion apparatus to a proper height depending variations in the depth of the sea are controlled by an independent hydraulic system, so the cost of the stern propulsion apparatus and hydraulic system are high. Furthermore, when the conventional stern propulsion apparatus for a boat of 5 tons or less is designed to generate 300 HP so as to meet the recent demand for high speed, the capacity of its hydraulic motor is enlarged, thereby increasing the hydrodynamic resistance of the stern propulsion apparatus.

[0006] Furthermore, in the conventional stern propulsion apparatus that is directly driven by a main engine, a lifting angle is confined to 60° or less and breakdown easily occurs owing to the necessity for additional reduction gear and reverse gear.

SUMMARY OF THE INVENTION

[0007] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a parallel-operated hydraulic motor type stern propulsion apparatus and hydraulic system for controlling the same, which is capable of reducing the hydrodynamic resistance of the apparatus that causes 80% of the required power, by employing two hydraulic motors each having half the required capacity and parallel-operated propellers.

[0008] Another object of the present invention is to provide a parallel-operated hydraulic motor type stern propulsion apparatus and hydraulic system for controlling the same, which is capable of reducing the mounting area, mounting costs and weight of the stern propulsion apparatus, effectively utilizing energy and simplifying the hydraulic system, by effectively utilizing a hydraulic system for operating the stern propulsion apparatus so as to operate steering and lifting devices.

[0009] In order to accomplish the above object, the present invention provides a parallel-operated motor type stern propulsion apparatus for boats, comprising: a transom box disposed at the stern of a boat; a propulsion body situated in the transom body to be lifted and steered, the propulsion body including, an upper body supported by a lifting shaft transversely fitted into the transom box, a yoke connected to the lower body, and two lower bodies each attached to each of the lower ends of the yoke; two hydraulic motors each positioned in each of the lower bodies and each connected to a propeller; lifting cylinders attached to the transom box for lifting the propulsion body around the lifting shaft; and a steering cylinder attached to the transom box for steering the propulsion body around a steering pin attached to the lifting shaft to the right and left.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0011]FIG. 1 is a view showing the construction of the parallel-operated hydraulic motor type stern propulsion apparatus;

[0012]FIG. 2 is a side view showing the stern propulsion apparatus in a state in which a propulsion body is lifted at a certain angle while being attached to the transom box;

[0013]FIG. 3 is a side view showing the stern propulsion apparatus;

[0014]FIG. 4 is a plan view showing the stern propulsion apparatus;

[0015]FIG. 5 is a hydraulic circuit diagram showing a hydraulic system used to control the forward and rearward drives, moving speed and lifting angle of the stern propulsion apparatus;

[0016]FIG. 6 is a view showing the construction of the control panel used to remotely control the stern propulsion apparatus; and

[0017]FIG. 7 is a partial cross-section showing a propeller shaft disposed between each hydraulic motor and each propeller.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.

[0019] A parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same is constructed as illustrated in FIGS. 1 to 7. In these drawings, reference numeral 1 designates a main engine.

[0020]FIG. 1 is a view showing the construction of the parallel-operated hydraulic motor type stern propulsion apparatus.

[0021] In the parallel-operated hydraulic motor type stern propulsion apparatus, a working fluid is supplied through a hydraulic hose (not shown) from a hydraulic pump 2 situated beside the main engine 1 to the stern propulsion apparatus, each of its propeller shafts is separated from each hydraulic motor shaft so as to allow its propellers and connection manner to be changed without changing the hydraulic motor shaft, the propellers are each provided at the end of the propeller shaft, a lifting shaft 12 is mounted to be inserted into the sidewalls of a transom box 4, and an upper body 52 and a steering pin 15 are provided at the center of the lifting shaft 12, thereby allowing the steering and lifting angles of the stern propulsion apparatus to be controlled.

[0022] Two hydraulic pumps 2 and 20 are connected in series to the main engine 1 situated in a sealed engine room. Two hydraulic motors 8 are each connected to each of the hydraulic pumps 2 and 20 so that a working fluid discharged from the hydraulic pumps 2 and 20 is supplied to the hydraulic motors 8 through the upper body 52, yoke 54 and lower body 56 of the stern propulsion apparatus. Two lifting cylinders 14 and a steering cylinder 18, situated on the sidewalls and top of the transom box 4 are each connected to each of the hydraulic pumps 2 and 20 so that a working fluid discharged from the hydraulic pumps 2 and 20 is supplied to the lifting cylinders 14 and the steering cylinder 18 through a hydraulic hose (not shown). A propulsion body 50 is situated in the interior of the transom box 4 attached to the stern wall of a boat through an opening utilizing a lifting shaft 12 and a steering pin 15.

[0023] A change in speed, forward and rearward drives and adjustment of steering and lifting angles of the stern propulsion apparatus can be accomplished through a hydraulic system shown in FIG. 5 by the manipulation of a control panel shown in FIG. 6.

[0024] The steering angle can be controlled within a range of +30° through a steering lever 16 shown in FIG. 4 and connected to the steering cylinder 18 and a steering link 17 shown in FIG. 1, utilizing a working fluid, which is supplied from the hydraulic system as a steering wheel 27 is turned clockwise and counterclockwise. The lifting angle can be controlled within a range of ±90° through a lifting lever 13 connected to two lifting cylinders 14 and a lifting shaft 12 to which the lift lever 13 is attached, utilizing a working fluid, which is supplied from the hydraulic system as a speed-change and reverse lever 34 is turned clockwise and counterclockwise.

[0025]FIG. 2 is a side view showing the stern propulsion apparatus in a state in which the propulsion body 50 is lifted at a certain angle while being attached to the transom box 4. The lifting shaft 12 supported by two bearings positioned in holes (not shown) formed in the transom box 4 is connected to the lifting cylinders 14 through the lifting levers 13 each being positioned on the side of the transom box 4.

[0026] The lifting levers 13 are each fixedly attached to the lifting shaft 12, and the lifting shaft 12 is fixedly connected to the upper body 52, thereby allowing the upper body 52 to be lifted and lowered.

[0027] The hydraulic motors 8 are each situated in each of the lower bodies 56 of the propulsion body 50. Two propellers 11 are each connected to a single hydraulic motor 8 by a single propeller shaft 9. In detail, the propeller shaft 9 is connected to the hydraulic motor shaft (refer to FIG. 7, 40) utilizing keys 41 and a lengthy bolt 42.

[0028] In order to reduce the weight of the stern propulsion apparatus, the transom box 4, the upper body 52, the yoke 54 and the lower body 56 are preferably made of aluminum except for the hydraulic system with which a high-pressure working fluid is brought into contact. The hydraulic motors 8 and the propeller shafts 9 are preferably made of high tensile steel of high strength in consideration of the high-pressure working fluid and rotational torque.

[0029] As shown in FIG. 2, the working fluid reduced in pressure to 30 atmospheric pressure through the pressure reduction valve 24 and the solenoid valve 29 of the hydraulic system is supplied to the two lifting cylinders 14 secured to the sidewalls of the transom boxes 4, the lifting cylinders 14 are connected to the two lifting levers 13, the lifting levers 13 are remotely controlled up and down by the solenoid valve 29 operated by manipulation of the lifting switch 35 of the control panel 35, and the propulsion body 50 attached to the lifting shaft 12 in the transom box 4 is lifted and lowered within 90 degrees depending upon the rotation of the lifting shaft, thereby adjusting the position of the propulsion body 11 properly.

[0030] As illustrated in FIG. 3, the transom box 4 and the upper body 52 are assembled together through the lifting shaft 12, the upper body 52 and the lower bodies 56 are connected by the inverse U-shaped yoke 54 so as to space the propellers 11 apart, the steering lever 16 and the steering cylinder (refer to FIG. 4, 18) connected to the steering link 17 are provided on the upper surface of the transom box 4, and the lifting levers 13 and the lifting cylinders 14 connected to the lifting shaft 12 are provided on the sides of the transom box 4, thereby allowing the propulsion body 50 to be steered to the right and left and to be lifted and lowered.

[0031]FIG. 5 is a hydraulic circuit diagram showing the hydraulic system used to control the forward and rearward drives, moving speed and lifting angle of the stern propulsion apparatus.

[0032] The hydraulic pumps 2 and 20 operated by the main engine 1 are mounted in the same casing. That is, the gear type circulation pump 20 is disposed beside the hydraulic pump 2 to be operated at the same number of rotations as that of the hydraulic pump 2. The circulation pump 20 supplies a working fluid, which is reduced in pressure to 30 atmospheric pressure by the pressure reduction valve 24, to a pilot valve 22 (operated by the speed-change and reverse lever 34), a servo cylinder 21 and a steering valve 28 through a second fluid supply passage. A working fluid supplied to the two hydraulic motors 8 for operating the propellers 11 is adjusted to 30° atmospheric pressures through relief valves 23 situated in reverse directions on a first fluid passage 61. While the stern propulsion apparatus is operated continuously, the increase in temperature and reduction in viscosity of the working fluid is prevented by cooling the working fluid discharged from the relief valves 23 and the pressure reduction valve 24 by fluid cooler 26. Impurities contained in working fluids sucked from an oil tank 30 to the pump 2 and 20 and returned to the oil tank 30 are removed in a suction filter 31 and a return filter 25. When a working fluid stored in the oil tank 30 leaks, the hydraulic system is replenished with a working fluid through a replenishment inlet 33.

[0033] In order to drive a boat forward or rearward by changing the rotating directions of the propellers 11 directly connected to the hydraulic motors 8, the operation of the pilot valve 22 and the servo valve 21 should be controlled by manipulation of the speed-change and reverse lever 34 situated on the control panel. The moving speed of the boat can be controlled by the operational speed of the main engine 1.

[0034]FIG. 6 is a view showing the construction of the control panel used to remotely control the stern propulsion apparatus.

[0035] The control panel includes pressure gauges 36 and 37 for indicating the pressures of the working fluid and cooled seawater, an indicator for indicating the temperatures of the working fluid and the cooled seawater and the rotational speed of the main engine and monitoring the electric charge of a storage battery for starting the main engine, and a starting and stopping switch for the main engine. The starting and stopping of a bilge pump for discharging bilge, the speed control of the main engine, the forward and reward drives and lifting and steering angles of the stern propulsion apparatus should be controlled by the control panel.

[0036] The speed-change and reverse lever 34 is used to remotely control the moving speed of a boat and the forward and reward drives, a bilge pump switch 38 for switching the power source of a storage battery, on and off is used to starting and stopping a bilge pump situated in the engine room, and a lifting switch 48 for switching the power source of the solenoid valve 29 is used to lift the stern propulsion apparatus.

[0037]FIG. 7 is a partial cross-section showing the propeller shaft disposed between each hydraulic motor and each propeller. Two keys 41 each having a rectangular cross-section are disposed on the tapered portions of each hydraulic motor shaft 40, the propeller shaft 9 is fitted over the keys 41 disposed on the tapered portion of the hydraulic motor shaft 40, and a bolt 42 is secured to the hydraulic motor shaft 40 after passing through the propeller shaft 9. All of these elements should be made of stainless steel so as to prevent corrosion due to contact with seawater.

[0038] In the parallel-operated motor type stern propulsion apparatus of the present invention, the forward and rearward drives, lifting angle and steering angle of the stern propulsion apparatus can be remotely controlled by controlling a working fluid, which is supplied by the hydraulic pump 2 directly operated by the main engine in the engine room, through the remote control of the solenoid valve 29 operated by the speed-change and reverse lever 34, the steering handle 27 and the lifting switch 35.

[0039] When the stern propulsion apparatus is mounted to the rear wall of the boat and the steering and lifting angles of the stern propulsion apparatus are remotely controlled, the steering lever 16 mounted on the top of the transom box 4 is operated by the single steering cylinder 18 and the lifting levers 13 attached to the right and left ends of the lifting shaft 12 are operated by the two lifting levers 14. Accordingly, the steering pin 15 is perpendicularly assembled with the lifting shaft through a hinge situated on the top of the upper body 5 and the stern propulsion apparatus should be freely operated while being lifted.

[0040] In order to the change the speed and direction of a boat, the number of rotations and rotational direction of each propeller can be changed. These can be performed by adjusting the amount of fuel injection from the main engine and manipulating the speed-change and reverse lever 34 used to remotely control the pilot valve 22.

[0041] In brief, two hydraulic motors 8 used to operate propellers 11 are each mounted in each lower body 56. In order to reduce the area for mounting the apparatus and the weight of the apparatus, the lower bodies 56 are utilized as hydraulic motor casings. Each hydraulic motor 8 is comprised of a cylinder, a piston, a drive shaft, a wobble plate support, a bearing housing and a fluid supply conduit. Since each hydraulic motor shaft 40 and each propeller 11 are connected by a single propeller shaft 9, the sealing room 10 is provided so as to prevent seawater from entering the interior of the stern propulsion apparatus. If in a large13 scale hydraulic system discharging a working fluid of about 300 cc/rev in a certain direction, the rotational direction of the hydraulic motor is changed directly by the pilot valve 22, thus causing unstable operation and noise. Accordingly, in order to desirably control the working fluid depending on load conditions, relief valves 23 should be added. When a propeller having a proper diameter and pitch is selected through driving tests and, thereafter, the proper propeller is changed with an original one, the hydraulic motor shaft 40 and the propeller shaft 9 should be manufactured separately so as to prevent the entire hydraulic motor from being changed. Each hydraulic motor shaft 40 is connected to the propeller shaft 9 through the keys 41 disposed on one end of the hydraulic motor shaft 40 and the propeller shaft 9 is secured to the hydraulic motor shaft 40 by means of the lengthy bolt 42.

[0042] The working fluid of 300 atmospheric pressures used to operate the hydraulic motors 8 for operating the propellers 11 is supplied by the hydraulic pump 2 directly operated by the main engine situated at a certain position in the engine room. The adjustment in the amount of the working fluid and the change of the rotational direction are performed by the servo cylinder 21 operated by the manipulation of the speed-change and reverse lever 34 on the control panel.

[0043] When there is a concern that the stern propulsion apparatus may be damaged by submerged projections or the stern propulsion apparatus is repaired or changed, the stern propulsion apparatus can be lifted at 90°. When the stern propulsion apparatus is lifted, the working fluid is reduced in pressure to 30 atmospheric pressures by the pressure reduction valve 24, the working fluid is supplied to the two lifting cylinders 14 by operation of the solenoid valve 29 by means the lifting switch 35. In this case, when the steering handle 27 is turned clockwise or counterclockwise, the steering valve 28 under the control panel is directly operated and the working fluid reduced in pressure is supplied to the single steering cylinder 18, thereby steering the stern propulsion apparatus to the right or left.

[0044] In accordance with the present invention, the following advantages can be accomplished.

[0045] Since a speed reduction gear, a clutch, a reversing gear and a drive shaft are eliminated and only hydraulic pumps are included in the stern propulsion apparatus, the placement of an engine room is easily performed. When the output of the stern propulsion apparatus is increased over 300 HP, the hydrodynamic resistance of a lower body in which each hydraulic motor is mounted is reduced. Since a set of transom boxes, upper bodies and lifting and steering devices can be eliminated rather than two independent propulsion apparatuses each having half the required capacity, the weight of the stern propulsion apparatus, the area for mounting the stern propulsion apparatus and the manufacturing cost of the stern propulsion apparatus are reduced. Since a hydraulic motor shaft can be firmly connected to a propeller shaft in comparison with a conventional spline fashion, the stern propulsion apparatus does not vibrate owing to its imbalance and the stern propulsion apparatus and the propeller shaft are not loosed from the hydraulic motor shaft owing to the thrust and the variation in torque, thereby improving the durability of a shaft system.

[0046] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

What is claimed is:
 1. A parallel-operated motor type stern propulsion apparatus for boats, comprising: a transom box disposed at the stern of a boat; a propulsion body situated in said transom body to be lifted and steered, said propulsion body including, an upper body supported by a lifting shaft transversely fitted into said transom box, a yoke connected to said lower body, and two lower bodies each attached to each of the lower ends of said yoke; two hydraulic motors each positioned in each of said lower bodies and each connected to a propeller; lifting cylinders attached to said transom box for lifting said propulsion body around said lifting shaft; and a steering cylinder attached to said transom box for steering said propulsion body around a steering pin attached to said lifting shaft to the right and left.
 2. The stern propulsion apparatus according to claim 1, wherein the output shafts of said hydraulic motors are each connected to a propeller shaft in a taper manner utilizing keys, and said propeller shaft is secured to each of the output shafts of said hydraulic motors by a lengthy bolt, thereby facilitating a change of propellers.
 3. The stern propulsion apparatus according to claim 1, wherein said hydraulic motors each have half the required capacity.
 4. A hydraulic system for controlling a stern propulsion apparatus, comprising: a hydraulic pump and a circulation pump connected to the output end of a main engine in a boat; a first fluid supply passage for connecting said hydraulic pump to said hydraulic motors in parallel; a serve cylinder for controlling the rotational direction of said hydraulic pump by changing the inclined angle of the wobble plate of said hydraulic pump; a pilot pump situated on a second fluid supply passage for controlling the rotational direction of said serve cylinder; and a steering valve and a lifting valve situated on said second fluid supply passage for controlling the operation of said steering cylinder and said lifting cylinders, respectively.
 5. The stern propulsion apparatus according to claim 4, further comprising two relief valves, which are situated in opposite directions and can operate said main engine so as to restrict the maximum hydraulic force exerted on said hydraulic motors.
 6. The stern propulsion apparatus according to claim 4, further comprising a pressure reduction valve for reducing the pressure of said working fluid to a set pressure, said pressure reduction valve being situated on said second fluid supply passage. 